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1. Infection & Immunity > Enteric Gram-neg (part 1) > Flashcards

Enteric Gram-neg (part 1) Flashcards

ENTEROBACTERIACEAE

1
Q

What is the medical importance of the enteric family?

A

Indicator of fecal pollution of water
30% of hospital acquired cases (nosocomial infection)
Easily studied genetically
Difficult to treat with antibiotics

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2
Q

Physical characteristics of Enterobacteriaceae

A

Gram-neg, medium sized rods
Flagella if mobile
Non spore forming anaerobes

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3
Q

What are some non-motile Enterobacteriaceae?

A

Klebsiella and Shigella genus

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4
Q

Cultural characteristics of Enterobacteriaceae

A

Ferment glucose
Resistant to acid and bile

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5
Q

What makes Enterobacteriaceae toxic?

A

Lipid A
Lipid A + O polysaccs=Lipopolysaccharide (endotoxins) –> on their cell wall

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6
Q

Selective media used for Enterobacteriaceae

A

Unioculated MacConkey

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7
Q

Which Enterobacteriaceae are lactose fermenters?

A

E. coli, Klebsiella, Enterobacter
with a pink pigmentation

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8
Q

Which Enterobacteriaceae are non-fermeters?

A

Salmonella, Shigella
with straw colored colonies

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9
Q

What are gram inhibitors?

A

Dye crystal violet that suppresses unwanted Gram-pos organisms by bile salt or bacteriostatic dye

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10
Q

Triple Sugar Iron (TSI)

A

Indicator media
Tests organisms for carb fermentation, gas production, hydrogen sulfide production

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11
Q

How do you categorize TSI?

A

Black= H2S
Cracks= Gas
Red slant= glucose used (no lactose and peptones used)
Yellow= all sugars fermented

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12
Q

How is salmonella and proteus classified by the TSI?

A

Slant= alkaline (red)
Butt= acid (yellow)
Gas (cracks) and H2S (black) positive

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13
Q

How is Enterobacteriaceae divided?

A
  1. Major pathogens
  2. Opportunistic pathogens
  3. Organisms of uncertain significance
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14
Q

Major pathogens

A

Salmonella
E. coli
3 Yersinia species

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15
Q

Opportunistic pathogens

A

Klebsiella, Enterobacter, Proteus, Edwardsiella, Citrobacter, Morganella, Shigella

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16
Q

There are over ______ genera and over ______ species

A

40
180

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17
Q

Escherichia coli (E. coli)

A

Ferments lactose
165 O chains, 50 H (flagella), 90 K (capsules) strains = over 1000 strains

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18
Q

Habitat of E. coli

A

Large and small intestine of mammals
Excreted in feces and can survive in dust, water and fecal particles for months
E. coli in water= fecal pollution

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19
Q

Adhesions

A

Fimbira/pili
Mediate adherence to the target cells (glycoprotein) in the GI tract

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20
Q

Capsules

A

Protects E. coli from complement cascade and inhibits microbe from attaching to phagocytic cells

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21
Q

What enterotoxins does E. coli produce

A

Heat liable toxin (LT)
Heat stable (STa and b)
Entero-aggregative heat stable (EAST 1)

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22
Q

How do enterotoxins affect cells?

A

Affect control of cyclic nucleotide activity within the affected cell –> deregulation of water and electrocytes

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23
Q

Predisposing causes of E. coli

A

Neonates obtaining insufficient Abs from colostrum
Intensive husbandry system
Poor hygiene
Stress factors

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24
Q

Why are neonates susceptible to E. coli?

A

Normal flora of intestine not fully developed
Naive immune system
Receptor for adhesions of enterotoxigenic present @ 1st weeks of calf life and 6 weeks for piggies

25
Q

White Scours (Colibacillosis) in young calf

A

1-5 days: E. coli
5-14 days: Rota- corona virus
10-30 days: Cryptospordium parvum
Any age; Salmonellosis, C. perfringens

26
Q

Edema disease in young weaning pig

A

Recent change in feed (lose maternal Abs)
Mild diarrhea noticed few days before

27
Q

How is E.coli classified?

A

E. coli causing intestinal disease or extra-intestinal disease

28
Q

Which E. coli strains cause intestinal disease

A

Enterotoxigenic E. coli (ETEC) &
Attaching and Effacing E. coli (AEEC)
|
v
Enteropathogenic E. coli (EPEC) &
Vero- Shiga- toxin producing strains (VTEC or STEC)
|
v
Enterohemorrhagic E. coli (EHEC) &
Strains of E. coli causing edema disease

29
Q

Enterotoxigenic E. Coli (ETEC)

A

Neonatal calibacillosis in calves, lambs and piglets - first week of life
Host specific
Produces watery diarrhea

30
Q

Pathogenicity of Enterotoxigenic E. coli

A

Adhesion followed by production of enterotoxins
Adherence mediated by fimbriae in pigs and calves

31
Q

Fimbrae receptors for Enterotoxigenic E. coli

A

F4 (K88), F5(K99), F6(987p), F17, F18, F41

32
Q

What is significant about Enterotoxigenic E. coli?

A

No gross or microscopic damage to enterocytes

33
Q

Toxins within Enterotoxigenic E. coli

A

LT (heavier)- stimulates cAMP causing secretions of fluids K+, Cl-, enterocytes
ST (smaller)- deregulate cGMP causing fluid and e-accumulation in bowel lumen

34
Q

Enteropathogenic E. coli (EPEC)

A

Within attaching and effacing E. coli (AEEC)
Causes muccoid diarrhea in piglets, lambs and pups by erasing normal structure of intestinal vili (no absorption and losing electrolytes and fluid)

35
Q

What are virulence factors of enteropathogenic E. coli encoded by?

A

Pathogenic island called enterocyte effacement

36
Q

Intimin

A

A key signaling factor of enteropathogenic E. coli that promotes close attachment of E. coli with enterocytes

37
Q

Shigatoxigenic E. coli (STEC or VTEC)

A

Edema disease in pigs associated with O139 and O141
Hemolytic and produce shiga toxin

38
Q

O139 and O141 strains

A

Present in the large intestine of pigs
Multiply rapidly under conditions of stress (change in diet)

39
Q

What are the 2 subtypes of the shiga toxin?

A

STx1 and STx2 (STX2e is associated with the edema disease in pigs)

40
Q

What does shigtoxigenic E coli target?

A

Endothelial cells of small arteries of the forehead, eyelids and mesentary

41
Q

What produces the shigo disease?

A

Heavy grain diet –> doesn’t produce enough saliva –> makes it easy for the bacteria to invade

42
Q

Enterohemorragic E. coli (EHEC)

A

Cause of food poisoning in humans
Associated with cases of hemorrhagic enteritis in calves

43
Q

What does eneterohemorragic E. Coli do?

A

Binds and effaces microvilli and produces shiga toxin
Damages adjacent cells and enters circulation

44
Q

What strains cause extra-intestinal disease?

A

Septicemic E. coli (SEPEC)
Uropathogenic E. coli (UPEC)
Avian pathogenic E. coli (APEC)
Mammary pathogenic E. coli (MPEC)

45
Q

Septicaemic E. coli

A

Frist step: adherence to the intestinal lining
Fimbriae, capsule, aerobactin (iron), endotoxin, colicin V, cytotoxic necrotizing factor, cytolethal factor

46
Q

How do you diagnose enterotoxins ST and LT?

A

ELISA

47
Q

How do you diagnose fimbral antigens?

A

Latex plate agglutination

48
Q

Diagnosis of EPEC E. coli

A

Demonstration of urease production
Ileum shows distortion of microvilli and effacement of mucosal surface

49
Q

Diagnosis of edema disease

A

Clinical and post-mortem findings
Isolates are hemolytic

50
Q

Antimicrobial resistance

A

Resistance to at least 2 classes of antimicrobial agents is common in vet med
Emergence of fluoroquinolone resistance

51
Q

How do you determine resistance?

A

Disc diffusion method or MIC for broth dilutions

52
Q

The genus enterobacter

A

Gram-neg bacilli, short and motile
Recovered from bovine mastitis, navel ill/neonatal septicemia, equine uterine infection, canine UTI

53
Q

Opportunistic pathogens under enterobacter?

A

Enterobacter aerogenes and E. cloacae

54
Q

Diagnosis of enterobacter

A

Recovery of agent from clinical material and ID by biochem tests

55
Q

What is enterobacter resistant to?

A

Ampicillin, cephalothin and tetracyline

56
Q

The genus citrobacter

A

Widely distributed in the environment (soil, water)
Citrobacter rodentium
Transmissible murine colonic hyperplasia

57
Q

Where is citrobacter found?

A

Colon (descending) and cecum –> thickened mucsosa and increasing bowel size

58
Q

Diagnosis of citrobacter

A

PCR and culture

1. Infection & Immunity (19 decks)

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